From Reefcleaners link:
Diatoms
Almost sure to appear in a new system, diatoms are some of the most abundant organisms on earth. They usually surface in the aquarium as a brown powdery like substance, within a week or so after a tank finishes its cycle. Diatoms feed on available silicates in your system and will run their course in time. Similarly, because they feed on silicates, anytime you add new sand, rock or something plastic they can pop up.
Manual Removal: Diatoms are easily wiped from the glass with a mag float, a turkey baster or a toothbrush can access other areas of the tank. Be prepared for them to re-establish themselves quickly, they are likely to be able to resettle and have exponential growth rates.
Clean Up Crew: Ceriths, Nerites and Trochus and Astraea snails are effective at removing diatoms, as well as the algae species that usually replace them as the silicates in your system are depleted.
Green Film Algae, Film Algae
filmalgae 300x400
This green powdery film, or cloudiness is caused by a variety of species of microalgae. It is fairly common in tanks of all ages, and tends to be present in some degree at all times. It is only when a bloom occurs that the microalgae becomes so dense as to become noticeable.
Clean Up Crew: Ceriths, Nerites, Astraea spp., most limpets and chitons. Many different species of copepods, amphipods and isopods will feed on film algae as well. Hermit crabs pick at it but are rarely effective against film algae.
@Ads541
Zero nitrate and zero phosphate are not desirable. As a generalization, with low nutrients undesirables thrive and desirables suffer.
